The present invention relates to methods and apparatus for the processing of eggshells, and more particularly to such methods and apparatus which are particularly adapted for effectively separating the eggshell membrane from the outer eggshell in a manner that the separated fractions can be used effectively in food products and possibly other uses.
It is necessary that egg-breaking facilities must dispose of their waste eggshells in some manner, and many companies pay to have their eggshells trucked away to a garbage dump.
In other instances, the eggshells are put to use after being processed in some manner and one prior art method is as follows. After the eggs are cracked and the yolk and albumin are removed, there remains the cracked eggshell, comprising the outer eggshell portion along with the membranes attached thereto, and residual egg liquid. These eggshells are first placed in a centrifuge to get rid of the extra liquid, which can be used for some commercial purposes. In some instances, after liquid removal, the eggshells are used as landfill. In other instances, the eggshells are dried and ground, after which these are used by putting these back into a feed product for chickens.
The way this is accomplished in this prior art method is to first place the eggshells with the membrane in a rotary drum dryer, and this removes the water and also acts as a pasteurizer. From the dryer the eggshells are directed into a hammer mill, which may be conventional. The action of the hammer mill is such that this reduces eggshells to a relatively fine powder.
Then, in accordance with the prior art process, this powdered material, which combines most of the outer eggshells and the membrane are removed from the hammer mill and directed by a suitable conveyor to a collecting system. From there, the powder is taken to a location to be incorporated in the chicken feed product.
A search of the U.S. Patent literature disclose a number of patents which relate to the removal of eggshells from the eggs (the albumen and yolk), where the egg is either already cooked or raw. These patents are the following:
U.S. Pat. No. 4,308,290 (Fujii) discloses a method for peeling the shell from boiled eggs, where a hard-boiled egg is carried through a pipe by a fluid stream that breaks up the shell while the membrane remains unbroken. Then the shell membrane is broken by applying a whirling water stream and a centrifugal force generated by the circular motion.
U.S. Pat. No. 4,082,856 (Zwiep et al) shows a process and apparatus for shelling eggs. The apparatus can be more easily understood by examining FIG. 4 and the text beginning in Column 4, line 51, and continuing on through the first half of Column 5. The hard-boiled eggs first come into the hopper 11, then go through a vibrating chute 13 to crack the egg shell, then go through an orifice section where the shell (including the membrane) is stripped from the egg, then through scrubbing section 17, and finally through the table 19, which has a wire or grill surface. There is a spray at 21 which provides a final cleaning action. The meats 18 of the eggs (less the shells) are directed through a gathering chute 22. The trap or basket 23 gathers and separates the shell debris 16 from the process fluid. The shell fragments and the membrane fall into the container 23, and there is no other discussion as to how these are handled.
U.S. Pat. No. 3,774,525 (Driggs) Shows and apparatus for peeling eggs where the eggs are placed into a rotating cylinder. After the peeling cycle has been completed, so that the shell and the membrane are separated from the egg, the eggs and the shells are then deposited upon a rack which is designedxe2x80x9d . . . so that the eggs will roll over the rack to a collecting point while the cracked and broken shells will pass through the rack to a separate collection point. (Column 6, lines 30, 31-33).
U.S. Pat. No. 3,552,458 (Whitman) Shows an xe2x80x9capparatus for deshelling hard-cooked eggsxe2x80x9d. The eggs first go through an apparatus which cracks the eggshells, and then the removal of the shells is accomplished in the manner shows in FIG. 6, where the eggs are advanced along two rolls 73 and 75 by the belt 85. Jets of water are sprayed on the eggs by the pipes 95 to assist in the removal of the eggshells (presumably with the membrane).
U.S. Pat. No. 2,535,980 (Yeamans) discloses a xe2x80x9chard-boiled eggshell removerxe2x80x9d where the eggshell is crushed in a tapered cylinder. In Column 2, beginning on line 7, the last part of the process is described as follows:
xe2x80x9cAfter a few turns of the crank handle, the entire eggshell will be loosened and will fall off and the bare egg, with a clean, whole surface, is then ready to be removed from between the blades and replaced by another egg in its shell.xe2x80x9d
U.S. Pat. No. 2,548,812 (Patterson) Shows a centrifugal separator where the raw eggs are deposited into a rapidly rotating basket 12. The egg product flows outwardly through the holes, while the shells are retained within the basket 12. The egg material then flows downwardly through the passageway 21 into a collecting reservoir 23. When sufficient eggshells have accumulated in the basket 12, then the machine is stopped and the basket 12 emptied of the eggshells.
U.S. Pat. No. 498,488 (Power) discloses a machine and method for xe2x80x9cextracting the contents of eggsxe2x80x9d where the raw eggs are placed in a centrifuge which breaks the raw eggshells and separates the whites and yolks from the shells.
Also, there was disclosed in this search three patents relating generally to hammer mills and their operation. These three patents are the following:
U.S. Pat. No. 2,258,537 (Calkins) discloses a hammer mill having an improved construction of a screen to provide for portions of different mesh over the outlet opening of the grinding chamber of the mill.
U.S. Pat. No. 2,440,927 (Boss et al) shows a grinding mill of the hammer-type for grinding feed and the like with a screen which is adapted for remote control adjustment through a wide range.
U.S. Pat. No. 2,169,684 (Erickson) shows a hammer mill for grinding grains, coal, rock and like materials. This relates more to a novel feeding mechanism which will not become clogged by foreign matter.
The methods and apparatus of the present invention are particularly well adapted to the processing of eggshells so as to separate the components of the eggshell into a form where these could be used as commercially viable products. The present invention comprises several embodiments of the method, and also an apparatus particularly adapted for use in the present invention.
A first embodiment of the present invention is able to separate the eggshell components in a manner that membrane portions can be isolated as a separate product, and also the outer eggshell (comprising essentially calcium carbonate) can be isolated in a near pure form. Further, there can be generated a residual product made up of remaining outer egg shell particles along with some of the membrane.
In this first embodiment, the eggshells (comprising both the outer egg shell portions and the membrane portions) is dried to reduce the moisture content of the eggshells, and also cause at least some separation of the membrane portions from the outer eggshell portions.
Then a first amount of the membrane portions is separated from the eggshells to leave a remaining eggshell component that comprises an outer eggshell component and the remaining membrane portions. The separated membrane portions, could then be used as a commercial product, such as, for example, for use in the pharmaceutical industry.
The remaining eggshell component is directed to a processing chamber of a processing apparatus at an impacting zone. Then the remaining eggshell component is impacted in the chamber to reduce particle size of at least the outer eggshell component to form smaller, outer eggshell particles.
The smaller outer eggshell particles are collected at a collecting location, and a substantial portion of the remaining membrane portions are separated from outer eggshell particles. Also, some of the very small particles of the outer eggshell material (in the form of dust or nearly the particle size of dust) can be removed along with the remaining membrane portions that are processed in the processing chamber of the processing apparatus.
In a preferred form of the present invention, prior to separating the first amount of the membrane portions from the eggshells, the eggshells are agitated to break up the eggshells. Also, the agitating of the eggshells can be accomplished at the same time the eggshells are being dried. This can effectively be accomplished by drying the eggshells in a rotary drum dryer where a tumbling action is imparted to the eggshells to cause the further break up of the outer eggshell material.
Also in preferred form of the present invention, there is a washing of the eggshells prior to the drying of the eggshells to remove egg liquid therefrom. In a specific version described herein, prior to the drying step, the eggshells are subjected to both centrifuging and washing, thus removing egg liquid from the eggshells and also reducing the moisture content.
Further, in the preferred form, the first amount of membrane portions from the eggshells is accomplished by sieving the eggshells. This could be desirably accomplished by using a plurality of sieves, such as sieves having a U.S. mesh size of 6-12 mesh size. One arrangement that has been found to be satisfactory is three sieves having a U.S. mesh sizes of 6,7 and 10.
The impacting of the remaining eggshell component after having the first amount of membrane portions being removed therefrom (as described above) is, in a preferred form of the present invention, accomplished by moving a plurality of impacting members about an axis of rotation in the processing chamber. In general, these impacting members are moved in a circumferential path, and there is a positioning screen member at least partially around the circumferential path. Then as the smaller outer shell particles are formed, these pass through the screen member to descend to a lower portion of the processing apparatus to be collected. It has been found that in the present invention the smaller outer shell particles that are still collected are of a very high purity and are at least ninety seven percent or more calcium carbonate.
In a preferred form, these smaller screen particles are removed from the collecting location by selectively operating a discharge valve at the collecting location. Then the smaller outer eggshell particles descend by gravity through the valve.
Also in the preferred form, the remaining membrane portions along with very fine outer eggshell are removed from the chamber by removing these membrane portions particles and the very fine outer eggshell particles through a membrane portion discharge section. This is accomplished pneumatically by creating a pressure differential between an exit location of the inlet and the chamber. In a preferred form this is accomplished by a pneumatic discharge apparatus which creates a suction (i.e. lower pressure) at the inlet and carries the remaining membrane portions through a pneumatic conveyor.
In an exemplary embodiment of the present invention, the smaller outer eggshell particles that are collected have a particle size of about 600-900 microns. However, the apparatus and/or processing conditions could be varied so as to have larger or smaller particle size such as being as large as 1000, 1300, 1500, 1700, or up to 2000 microns, or as low as 500, 400, 300 microns or lower.
In a further version of the present invention, the smaller outer eggshell particles that are collected could be ground down to a much smaller particle size, to as low as 15 microns. At this particle size the outer egg shell particles (essentially calcium carbonate), when used as food product or a calcium supplement are generally not tasted by the person consuming these. However, the particle size could be made smaller, such as low as 13, 11, 9, 7, or 5 microns. Present analysis indicates that for the presently contemplated applications this reduction to smaller particle sizes would not provide any real benefit, but for some applications it might. Also, it this micron size could be larger such as 17, 19, 21 23, or 25 microns or higher. Again, this may be desirable for some applications, but these larger sizes are believed to be less desirable for use in human food products.
In a second embodiment of the present invention, the eggshells are first dried to reduce the moisture content of the eggshells and cause at least some separation of the membrane portions from the eggshell portions. Then the eggshells are subjected to a sieving process to separate an amount of the membrane portion from the eggshell. Then the membrane portions that are separated are then collected, and then these could be used for various commercial applications. These steps can be implemented in essentially the same manner as described above, including the addition of preferred versions of the same.
In a third embodiment, the eggshells are dried to reduce moisture content of the eggshells and cause at least some separation of the membrane portions from the outer eggshell portions. Then the eggshells are directed to an impact zone of a processing chamber of a processing apparatus, where the eggshells are impacted in the chamber to reduce particle size of at least the outer eggshell portions to form smaller outer eggshell particles. These can be discharged as described previously herein, and also the membrane portions can be removed pneumatically as described previously herein. These steps can be accomplished in substantially the same manner as described above, and in the preferred versions.
The apparatus which is adapted to be used in the present invention comprises a housing which has a processing chamber which comprises a circumferential wall portion which surrounds the chamber, and oppositely positioned side wall sections, which side wall sections, with the circumferential wall section, define the processing chamber. There is an inlet portion to direct the eggshells into the chamber.
The apparatus comprises an impacting portion positioned in an impacting zone of the chamber. This impacting portion comprises at least one impacting member which is rotatably mounted in the chamber to travel a circumferential path to impact the eggshells, so as to break up the eggshells and reduce particle size of at least the outer eggshell portions to form smaller eggshell particles separated from the membrane portions. The apparatus has an outer eggshell particle collecting area positioned below the impact zone to collect the smaller outer eggshell particles at least in part by gravity.
There is a pneumatic outlet portion to pneumatically remove membrane portion particles from the chamber.
In the preferred form, there is a plurality of impacting members which are rotatably mounted about an axis of rotation in the chamber. The impacting members move in a generally circumferential path, and there is further a positioning screen extending at least partially around a circumferential path so that outer eggshell particles pass through the screen member to descend to a collecting location at a lower portion of the processing apparatus. The apparatus further comprises a discharge valve at the collecting location for selectively removing the smaller outer eggshell particles.
Also the present invention includes the products resulting from the methods of the present invention, these products including the outer eggshell particles of a relatively high priority collected from the processing apparatus, and also the membrane portion or fraction derived form the separating (specifically sieving) process.
Other features of the present invention will become apparent from the following detailed description.